Verify huge email lists for free with Ruby

As the "tech guy" in my circle of friends I get approached from time to time with questions of all sorts from my less inclined pals. "Can you build me an app?", "What's Bitcoin?", "Do you have a bootleg copy of Photoshop?" being the most common. Of course, like any self respecting "tech guy" I generally ignore these and continue on with my life.

Recently one of these friends approached me with something I found interesting. He had acquired a rather large list of email addresses over the years relating to his business but had never marketed to them. He wanted to start promoting to these people, but was hesitant about using the list of 400,000 emails or so because it had been so long since they were collected.

If you're not familiar — many email delivery systems (SendGrid, CampaignMonitor, MailChimp) will blacklist you or disable your account if you try marketing to a huge list and a large percentage of those addresses are invalid. He mentioned looking into programs that could perform that service for him, but all of them seemed prohibitively expensive.

Here's a selection of the better services I found for email address verification…

Because the script ultimately needs to connect to SMTP (email) servers, there are issues that you can run into — namely getting banned for connecting too fast, or performing too many validations…

Cloud Proxy Generator

Due to the issue explained above, I created Cloud Proxy Generator — which generates a number of SOCKS 5 proxies that you can then feed to Email List Cleaner to multiplex your connection. This has a few benefits…